The present invention generally relates to an apparatus, and system and/or method capable of charging (or recharging) batteries, and more particularly, but without limitation, to an apparatus, and system and/or method that may be capable of minimizing its power dissipation requirements by adjusting the magnitude of the charging current being sent to the batteries being charged—based, in part, on each battery's level of charge.
Generally, rechargeable batteries are available in a variety of chemical configurations including the “old standard” lead-based, car batteries, and the “newer” nickel cadmium, nickel metal hydride and “lithium” rechargeables. Furthermore, because rechargeable batteries may be able to provide cost savings (by eliminating the need to purchase a new battery each time an old battery becomes depleted) these batteries are being produced in a variety of shapes and sizes, and for use in a growing number of applications.
Consequently, differing types of battery chargers have been developed, and many of these are well known in the prior art including low charge-rate, timed, and rapid chargers. While many of these chargers are generally adequate, charging problems may still arise due to various design constraints. As examples, the low charge-rate charger may take an inconvenient amount of time to complete its task; the timed charger may complete its “timed charging cycle” before the batteries that are being charged are actually fully charged; and the rapid charger may overcharge and possibly ruin a battery. Regarding this, and as an example, rechargeable lithium-ion batteries are intolerant to overcharge conditions, and may experience early cycle life failures. This overcharging problem is heightened in applications that are configured to charge multiple series-connected batteries from a common charging source. In such configurations, some of the batteries being charged may become fully charged earlier then others, which may subject these batteries to an overcharge condition that could shorten their cycle life. However, because it is usually less expensive to charge multiple batteries from a single source than it is to provide a separate charge source for each individual battery being charged, a common charge source may be preferable.
In response, new technologies are emerging, and one such technology uses shunt style charging circuits to clamp the charging voltage of each series connected battery to a “precise” predetermined voltage setting. Generally, these charging circuits shunt excess current around each series connected battery while essentially holding each battery's voltage constant at some predetermined voltage level. A benefit of using shunt regulators is that they are inexpensive to build and are able to achieve precise charge voltage levels. On the other hand, however, they are very inefficient in operation because of the large amounts of power that they dissipate during the shunting action. Moreover, while shunt regulators are usually designed to dissipate full power for extended periods-of-time, the use of these higher power levels may shorten the lifetime of any associated electronic circuitry and may require the addition of some form of supplemental cooling.
Therefore, a need exists for the development of an efficient, shunt-type battery-charging device that is designed to reduce the likelihood of overcharging and the possible deleterious effects (and cooling requirements) associated with the generation of heat during the charging process.